Boundedness of the Kitanidis Filter for Optimal Robust State Estimation

The Kitanidis filter is a natural extension of the Kalman filter to systems subject to arbitrary disturbances or unknown inputs. Though the optimality of the Kitanidis filter was founded for general time varying systems more than 30 years ago, its stability analysis is still limited to time invariant systems, to the author's knowledge. In the framework of general time varying systems, this paper establishes upper bounds for the error covariance of the Kitanidis filter and for all the auxiliary variables involved in the filter.